4 files changed, 58 insertions, 27 deletions
diff --git a/include/elna/boot/name_analysis.h b/include/elna/boot/name_analysis.h
index 9e10fab..a9e7f24 100644
--- a/include/elna/boot/name_analysis.h
+++ b/include/elna/boot/name_analysis.h
@@ -63,7 +63,7 @@ namespace elna::boot
      * \c const qualifier used incorrectly — wrong position or
      * duplicate.
      */
-    class name_analysis_error final : public error
+    class const_qualifier_error final : public error
     {
     public:
         enum class kind
@@ -77,7 +77,7 @@ namespace elna::boot
         };
         using payload_type = std::variant<not_initialized, kind>;
 
-        name_analysis_error(const source_position position, payload_type payload);
+        const_qualifier_error(const source_position position, payload_type payload);
         std::optional<std::pair<std::string, source_position>> note() const override;
 
         std::string what() const override;
diff --git a/include/elna/boot/result.h b/include/elna/boot/result.h
index 03d589e..bf2149a 100644
--- a/include/elna/boot/result.h
+++ b/include/elna/boot/result.h
@@ -184,6 +184,19 @@ namespace elna::boot
     };
 
     /**
+     * Creates an error note pointing to a previous declaration.
+     *
+     * \param original Source position of the previous declaration.
+     * \param label Description what was declared previously.
+     * \return Error note if the position of the previous declaration is available.
+     */
+    std::optional<std::pair<std::string, source_position>> previous_declaration_note(
+            const std::optional<source_position>& original, std::string_view label = "previously declared here");
+
+    std::optional<std::pair<std::string, source_position>> identifier_list_note(
+            const std::vector<identifier>& identifiers);
+
+    /**
      * Checks whether the givn object can be converted to a string using
      * the .to_string() method.
      */
diff --git a/include/elna/boot/type_check.h b/include/elna/boot/type_check.h
index 93e891a..52eec61 100644
--- a/include/elna/boot/type_check.h
+++ b/include/elna/boot/type_check.h
@@ -58,14 +58,8 @@ namespace elna::boot
         {
             integer_literal overflow;
         };
-        enum class kind {
-            record_base,
-            for_range,
-            condition,
-            constant_assignment,
-            array_index,
-            non_indexable,
-            dereference_of_non_pointer
+        struct constant_assignment
+        {
         };
         using payload_type = std::variant<
             expected_type,
@@ -74,7 +68,7 @@ namespace elna::boot
             binary,
             invalid_cast,
             integer_literal_overflow,
-            kind
+            constant_assignment
         >;
 
         type_mismatch_error(const source_position position,
@@ -87,6 +81,29 @@ namespace elna::boot
         payload_type payload;
     };
 
+    class type_requirement_error : public error
+    {
+    public:
+        enum class kind
+        {
+            record_base,
+            for_range,
+            condition,
+            array_index,
+            non_indexable,
+            dereference_of_non_pointer
+        };
+
+        type_requirement_error(const source_position position,
+                type actual, kind kind);
+
+        std::string what() const override;
+
+    private:
+        type actual;
+        kind m_kind;
+    };
+
     /**
      * Cyclic type declaration.
      */
@@ -95,7 +112,7 @@ namespace elna::boot
         std::vector<std::string> cycle;
 
     public:
-        cyclic_declaration_error(const std::vector<std::string>& cycle, const source_position position);
+        cyclic_declaration_error(const source_position position, const std::vector<std::string>& cycle);
 
         std::string what() const override;
     };
@@ -106,12 +123,22 @@ namespace elna::boot
      */
     class argument_count_error final : public error
     {
+    public:
+        enum class kind
+        {
+            trait,
+            call,
+            array
+        };
+    private:
+        kind m_kind;
+        std::string applicand;
         std::size_t expected;
         std::size_t actual;
 
     public:
-        argument_count_error(std::size_t expected, std::size_t actual,
-                const source_position position);
+        argument_count_error(const source_position position, kind kind,
+                std::string applicand, std::size_t expected, std::size_t actual);
 
         std::string what() const override;
     };
@@ -122,18 +149,15 @@ namespace elna::boot
     class trait_error final : public error
     {
     public:
-        struct argument_count
+        struct offset_not_field_name
         {
-            std::size_t expected;
-            std::size_t actual;
         };
-        struct offset_not_field_name {};
         struct unsupported_type
         {
             type actual;
         };
 
-        using payload_type = std::variant<argument_count, offset_not_field_name, unsupported_type>;
+        using payload_type = std::variant<offset_not_field_name, unsupported_type>;
 
         trait_error(const source_position position, const std::string& trait_name,
                 payload_type payload);
diff --git a/include/elna/boot/validation.h b/include/elna/boot/validation.h
index 171ac1d..65972b7 100644
--- a/include/elna/boot/validation.h
+++ b/include/elna/boot/validation.h
@@ -30,19 +30,13 @@ namespace elna::boot
     class validation_error final : public error
     {
     public:
-        struct duplicate_case
-        {
-            source_position first;
-        };
-        using payload_type = std::variant<duplicate_case>;
-
-        validation_error(const source_position position, payload_type payload);
+        validation_error(const source_position position, source_position first);
 
         std::string what() const override;
         std::optional<std::pair<std::string, source_position>> note() const override;
 
     private:
-        payload_type payload;
+        source_position first;
     };
 
     /**